The formation of hard baked-on food soils on surfaces of food preparation units has been a problem faced by institutional cleaning personnel and household individuals for many years. During cooking, food soils commonly come into contact with heated metallic or porcelain surfaces in food preparation units. The food soils, containing various proportions of inorganic materials and of organic proteinaceous, fatty or carbohydrate soils, can become baked-on and can become hard or can be carbonized. Such soils are very difficult to remove, require substantial energy input during cleaning and often require very high concentrations of harsh disagreeable cleaning materials. A substantial need has existed in this art for solutions, other than using stronger cleaners, to improve the effective removal of such soils.
One attempt to reduce the difficulty in removing these soils relates to the use of self-cleaning ovens that ash the soil at high temperatures. Self-cleaning ovens commonly contain a catalytic coating on the interior heated surface of the food preparation unit. Periodically, the food preparation unit is heated to a temperature of about 500.degree.-600.degree. F. At this temperature the catalytic surface is designed to promote the combustion and removal of the hard baked-on soils resulting in ashing the soil which then can be removed without difficulty. One example of such catalytic coatings is found in Stiles et al., U.S. Pat. No. 3,460,523, which is directed to a finely divided thermally stable oxidation catalyst.
Another attempt to reduce the difficulty in removing such baked-on soils is found in attempts to formulate barrier coatings that can be used on heated food preparation units. Examples of such materials include White et al., U.S. Pat. No. 3,196,027, who teach a hydrocarbon solvent containing a dimethyl polysiloxane. Hatch et al, U.S. Pat. No. 3,303,052, teach a hydrophilic synthetic tetrasilicic fluorine mica that is applied to a food preparation surface in the form of an aqueous aerosol used with a fluorocarbon propellant. Arnold, U.S. Pat. No. 3,877,972, teaches a metal phosphate polymer composition which is exemplified by an aluminum ethyl oleyl orthophosphate dissolved in hexane. Dimond, Canadian Patent No. 1,047,903, teaches an oven cleaner composition. The aqueous cleaner, which is not used as a barrier coating, uses as active cleaning ingredients, a substantial proportion of an aqueous base comprising a mixture of sodium hydroxide and monoethanol amine, a clay-like bentonite thickener with other ingredients to form an aerosol oven cleaner. Cockrell, Jr., U.S. Pat. No. 4,877,691 (PCT International Application No. PCT/US91/05092), teaches a pretreatment composition comprising an aqueous dispersion of an inorganic thickening agent such as a Veegum.RTM. clay, an inorganic water soluble salt such as sodium or potassium bicarbonate with a small amount of a wetting agent. Cockrell, Jr. states that the use of substantial quantities of organic material, in particular organic thickeners such as xanthan gums, are highly undesirable. Cockrell, Jr. states at Col. 11, lines 9-19, that the barrier coatings containing bicarbonate in the presence of xanthan thickeners have a tendency to decompose spontaneously at room temperature. The evolved carbon dioxide caused difficulty in dispensing the materials from spray containers. Further, the formulas when applied to heated food preparation units resulted in dried films that blistered, were riddled with holes and extremely fragile. The dried films flaked and became separated from the walls of the units. Substantial decomposition of the thickeners were noted.
Makiko et al., Japanese Patent Publication No. 03-038,254, teach a film that provides a hard slippery surface to permit removal of oily stains. The film comprises a layered structure compound and a solid inorganic oxide compound with a polysiloxane binder.
The materials used to form barrier coatings in ovens that promote the release of the baked-on fatty soils have had some success. However, the highly inorganic nature of certain materials renders the partially insoluble coatings difficult to dispense. Further, many barrier coatings, after a number of oven cycles tend to become hardened and difficult to remove with mild aqueous detergents. Lastly, many materials in the prior art tend not to form a sufficient barrier. In many instances, the coatings do not produce a sufficient barrier and do not sufficiently promote soil removal to be acceptable in many institutional or household environments.
A substantial need remains in the art to form an aqueous composition that can be applied to vertical or inclined surfaces to remain in place without sagging. The compositions should provide a thick layer which can act as a substantial barrier between the formation of hardened, carbonized baked-on fatty soils and heated surfaces. The barrier coatings and the baked-on soils should be easily removed without substantial difficulty with mild cleaning compositions.